This invention relates to a programmable sequence controller which is installed between a numerical control device and a machine such as a machine tool or robot. More particularly, the invention relates to a programmable sequence controller which permits a display of the data stored in a temporary storage circuit adapted to store the data which is exchanged with the machine through a data input/output unit, and which permits predetermined numerical values to be set in the temporary storage circuit from an external unit.
Numerical control systems permit various mechanical elements in machine tools, robots and other devices to be controlled on the basis of instructions from a numerical control device which incorporates an operation panel. It is necessary in such numerical control systems to provide circuitry between the numerical control device (referred to as an NC hereinafter) and the machine in order to transmit the NC commands to each of the mechanical elements. This is conventionally accomplished by the provision of heavy current circuitry comprising a multiplicity of relay groups, the relays being actuated in accordance with the NC commands such as M-function instructions, S-function instructions and commands from the operation panel. The conventional arrangement, however, incorporates a numerical control system which is large in size, and necessitates a large number of relays in order to handle more complicated operations. Higher costs and a decline in reliability are the result.
A proposed system for improving upon the foregoing arrangement employs a programmable sequence controller to perform the function of the relays. With a programmable sequence controller the processing of signals between the NC and machine is accomplished by way of the program, so that the problems of system size and operation complexity can be solved without a major increase in cost. Such an arrangement allows the operational status to be simply ascertained by providing a display of the data exchanged with the machine, and also permits data to be readily introduced from an external unit. Nevertheless, an increase in the cost and size of the system cannot be avoided with the conventional programmable sequence controller owing to the addition of the peripheral equipment such as the display devices and data setting devices provided exclusively for the controller.